This invention relates to an induction system for an internal combustion engine and more particularly to an induction system that offers improved engine performance throughout the performance range of the engine.
It has been recently discovered that the idle and low speed performance of an engine may be improved by delivering the mixture to the engine chambers under this running condition through a separate, relatively small sub or auxiliary passage. The use of the small auxiliary induction passage causes the intake mixture to enter the chambers at a substantially greater velocity to increase turbulence in the chamber at the time of ignition. This greatly improves the speed of flame propagation and combustion efficiency. As a result, the emission of unwanted exhaust gas constituents may be reduced and, at the same time, fuel economy increased.
The proportion of flow to the chambers through the auxiliary and main induction passages is controlled by one or more throttle valves which control the flow through at least one of these passages. It has been found that performance may deteriorate due to the induction of a volume of mixture which has been trapped between the closed valve of the main induction system and the chamber, which results in a reduction in induction velocity through the auxiliary passage.
It is, therefore, a principal object of this invention to provide an improved induction system for an internal combustion engine.
It is another object of this invention to provide an engine induction system that offers improved performance throughout the engine load range and good transitional performance.
In connection with an induction system of the type described, when applied to a multiple cylinder engine, the aforenoted effects may be avoided by interconnecting a portion of the auxiliary induction passages downstream of the control valve and with the main induction passage. In this way, a sub atmospheric pressure can be generated in the trapped volume for improving the air flow and minimizing the aforenoted effects.
In connection with the type of induction system previously described including main and auxiliary induction passages, it has also been found important to prevent leakage past the throttle valve which should be closed at idle and low load conditions. This assists in maintaining the sub atmospheric pressure as described in the preceding paragraph. Although this leakage can be substantially eliminated by maintaining an extremely good surface finish between the throttle valve and the passage which it controls, the geometry of the induction manifold may not always permit such machining. Furthermore, machining of the entire manifold surface to achieve this result is unduly expensive.
It is, therefore, a further object of this invention to provide an improved control valve system for the induction system of an internal combustion engine.
It is another object of the invention to provide an induction system control valve that affords good sealing at low cost.